如何在wagtail中以编程方式将页面添加到已知的父页面时添加标记？

from wagtail.core.models import Page
from wagtail.core.blocks import StructBlock, CharBlock
from wagtail.admin.edit_handlers import FieldPanel, StreamFieldPanel
from wagtail.core.fields import StreamField

class CustomPage(Page):
    # 定义一个StreamField来存储标记
    tags = StreamField([
        ('tag', CharBlock()),
    ])

    content_panels = Page.content_panels + [
        StreamFieldPanel('tags'),
    ]

    # 添加一个自定义的方法来将页面添加到已知的父页面并添加标记
    def add_page_with_tags(self, parent_page, title, tags):
        new_page = CustomPage(title=title)
        parent_page.add_child(instance=new_page)
        new_page.tags = tags
        new_page.save()

# 使用示例
parent_page = Page.objects.get(title='父页面')
title = '新页面标题'
tags = [
    ('tag', '标记1'),
    ('tag', '标记2'),
]
CustomPage().add_page_with_tags(parent_page, title, tags)